The invention relates to hinge joints in general, and more particularly to improvements in hinge joints which can be utilized with advantage in seats of vehicles, for example, in the drivers' seats of motor vehicles
Commonly owned U.S. Pat. No. 4,828,322 granted May 9, 1989 to Hansjorg WALK et al. for "Hinge joint for the seats of automotive vehicles and the like" discloses a hinge joint which can be used to change the mutual positions of two portions of a seat, e.g., the position of the back rest relative to the body supporting portion of a driver's seat in a motor vehicle. The patented hinge joint comprises first and second components which can be affixed to the body supporting portion and the back rest, respectively, and a device which pivotally connects the two components to each other and includes a shaft defining a pivot axis and including a cylindrical first portion which is journalled in one of the components, and first and second conical portions constituting fulcra for the other component. The first portion has an axis which is parallel to the pivot axis and the conical portions have a common axis which coincides with the pivot axis The patented hinge joint further comprises resilient means (e.g., a diaphragm spring) reacting against one of the components and biasing the coupling member in the direction of the pivot axis. Still further, the patented hinge joint comprises means (e.g., a spur gear and a mating internal gear) for releasably holding the components in selected angular positions relative to each other.
The shaft of the patented hinge joint is of one piece which contributes to its cost. Thus, the two conical portions and the cylindrical first portion of such shaft must be made of a single one-piece blank of high-quality metallic material. This contributes significantly to the cost of the shaft and of the entire hinge joint. In addition, the shaft must be machined with a very high degree of accuracy because the advantages (such as the elimination of radial play and adjustment with the exertion of a relatively small force) can be achieved only if the component parts, and particularly the shaft and the parts which are rotatably mounted on the shaft, of the patented hinge joint are machined and/or otherwise finished with negligible tolerances.
The disclosure of the patent to Walk et al. is incorporated herein by reference.